Evaluation of the treatment effect of rear slope cutting on hydrodynamic pressure landslides:A case study

After the impoundment of the Three Gorges Reservoir,some huge ancient landslides were reactivated and deformed,showing typical hydrodynamic pressure landslide characteristics.The Baishuihe landslide was a typical hydrodynamic pressure landslide.The management department conducted slope cutting treatments from 2018 to 2019.To evaluate the treatment effect of rear slope cutting,this study analyzed the data of the surface deformation survey and field monitoring over the past 20 years and the characteristics of the reservoir water-triggered Baishuihe landslide deformation,and calculated the seepage field,displacement field,and stability coefficient before and after landslide treatment.The results showed that the deformation of the Baishuihe landslide was primarily related to a decrease in the reservoir water level.Owing to the poor permeability of the landslide soil,the decrease in the reservoir water level produced a seepage force pointing to the outside of the landslide body,leading to the step deformation of the landslide displacement.The landslide was treated by rear slope cutting,and the“step”deformation of the landslide disappeared after treatment.The hydrodynamic pressure caused by the change in reservoir water after cutting the slope did not disappear.However,as the slope cutting greatly reduced the overall sliding force of the landslide,its stability was greatly improved.Notably,high stability can still be ensured under extreme rainfall after treatment.Slope cutting is effective for treating hydrodynamic pressure landslides.This study can provide effective technical support for the treatment of reservoir landslides.

Matrix test measurements of ground-borne vibration induced by the heavy-duty trains on embankment and cutting tracks in a loess area

This paper presents a comparative analysis of ground vibration in three directions generated by a heavy-duty railway with various track sections.The vibration characteristics in the plane area were investigated by using matrix test measurements.Acceleration peak attenuation was faster within 25 m from the embankment,and the high-frequency vibration attenuates faster with increased distance.For the cutting section with multi-stage soil slope,decay rate of acceleration was relatively larger.The acceleration level of the plane region ranged to 82.2-89.1 dB by the single C80 train.Yet the acceleration level caused by the C80 trains running parallel after meeting showed a distinct increment.The increment of the cutting section was much larger compared with the embankment section,with the increment ranging from 1.2-2.5 dB.In terms of the cutting section,Y direction acceleration was dominant closer to the track.Within 10-30 m of the track,the Y direction acceleration(perpendicular to the rail)decreased rapidly and became comparable to the X direction(parallel to the rail)and Z direction.Additionally,the cutting case generated a higher level of vibration in all three directions compared to the embankment,but as the distance from track increased,the deviation between acceleration gradually decreased.

Human-induced landslide on a high cut slope: a case of repeated failures due to multi-excavation

The paper attempts to represent a case of repeated failures on a high cut slope due to multi-excavation. The characteristics of each failure induced by excavation are analyzed through geological investigation, and then a geological model at different failure stages is proposed. The geological analysis shows that the excavation-induced repeated failures are related to the exposure of the weak bedding plane and the toe unloading of the cut slope, Numerical modeling is conducted based on a sequential method, taking into account the main failure stages of cut slope. The simulation results fairly coincide with the practical phenomena observed in field. It is shown that the decrease in normal stress of displaced mass on cut slope will induce the increase in shear stress in bedding planes and that at the toe of the cut slope. The released stress leads to repeated gravitational instabilities of cut slope due to the decrease in normal stress and the increase in shear stress along the bedding planes of mudstone.

Stability investigation of road cut slope in basaltic rockmass,Mahabaleshwar,India

Slope failures along hill cut road slopes are the major nuisance for commuters and highway planners as they put the human lives at huge risk,coupled with immense monetary losses.Analysis of these vulnerable cut slopes entails the assessment and estimation of the suitable material strength input parameters to be used in the numerical models to accomplish a holistic stability examination.For the present study a 60 m high,basaltic and lateritic road cut hill slope in Mahabaleshwar,India,has been considered.A number of samples of both basalt and laterite,in their natural state were tested in the laboratory and the evaluated maximum,minimum and mean strength parameters were employed for the three cases in a distinct element numerical model.The Mohr-Coulomb failure criterion has been incorporated in the numerical model for the material as well as the joints.The numerical investigation offered the factor of safety and insights into the probable deformational mechanism for the three cases.Beside,several critical parameters have also been judged from the study viz.,mode of failure,factor of safety,shear strain rate,displacement magnitudes etc.The result of this analysis shows that the studied section is prone to recurrent failures due to the capping of a substantially thick layer of weaker lateritic material above the high strength basaltic rock mass.External triggering mechanisms like heavy precipitation and earthquake may also accelerate the slope failure in this area.The study also suggests employing instant preventive measures to avert the further risk of damage.

Dynamic Design and Construction of Highway Cut Slopes in Huangshan Area, China

Deformation and failure of high slope impact the construction and operation safety of highway in the mountainous areas. The deformation and failure are mainly caused by poor design which normally has not well combined with the geological conditions and unplanned construction. Therefore, effective design and construction management should be conducted for ensuring a successful construction without damage and risk. In light of the reality of high slope construction along highway in the Huangshan area, this paper proposes a technical procedure for dynamic design and construction management of high slopes along highway in the mountainous area. The proposed construction management scheme is divided into three phases, i.e., 1) design phase, 2) preparation phase of excavation, and 3) construction phase. During the design phase, experiences and lessons learnt from the design and construction of other high slopes along highway in the same region are summarized. The number of slopes and slope height should be optimized from the aspects of route selection and route form. During the preparation phase of excavation, "Excavation Permit Management System" should be adopted, and construction scheme should be made by the construction unit, then the scientific research and design unit determine whether it guarantees slope stability and makes optimization measures. During the construction phase, the scientific research unit would make proposal of optimization design, and apply the achievements of scientific research into practice through common efforts of various units based on the understanding of excavation and investigation. The management system mentioned above is adopted to conduct dynamic design and construction management for more than 90 slopes along the Huangshan - Taling - Taolin Expressway, and successful results of application have been achieved.

Effect of the frozen layer on the stability of cut soil slopes during seasonal freezing and thawing

Research on the stability of soil slopes in seasonally frozen regions has mainly focused on slope failures during the thawing window.There are few studies on slope stability during the freezing window and its subsequent influence on slope failure in the next thawing window.In this paper,soil strength was tested during freezing and thawing to obtain temperature-dependent strength parameters for the simulation of slope stability.Then,the slope's temperature field over an entire year was accurately simulated so that characteristics of the frozen layer could be determined at any time.Based on the above results,the progressive failure modes of frozen soil slopes are discussed.The results show that:1)during the freezing window,depth of the frozen soil layer increases,as does the slope's safety factor,while a yield zone propagates towards the slope shoulder.(2)During the thawing window,the frozen soil layer shrinks in depth while the yield zone continuously expands,which decreases the safety factor.Comprehensive analysis of these results indicate that the frozen layer provides a“toe-locking effect”that increases the safety factor during the freezing window,while it also provides a“dragging effect”that propagates the yield zone towards the slope shoulder.During the thawing window,the“toe-locking effect”gradually diminishes;a continuous sliding surface is formed,which lead to a landslide.The frozen soil layer of the freezing window accelerates the slope sliding in the thawing window.

Practical studies on rockfall simulation by DDA

In this paper,simulations of real rockfall by discontinuous deformation analysis (DDA) are conducted.In the simulations,the energy losses of rockfall are categorized into three types,i.e.the loss by friction,the loss by collision,and the loss by vegetation.Modeling of the energy loss using absolute parameters is conducted by the DDA method.Moreover,in order to verify the applicability and validity of the proposed DDA,field tests on rockfall and corresponding simulations of rockfall tests by DDA are performed.The simulated results of rockfall velocity and rockfall jumping height agree well with those obtained from the field tests.Therefore,the new technique properly considers the energy-absorption ability of slope based on vegetation condition and shape of the rockfall,and provides a new method for the assessment and preventive design of rockfall.

From the new Austrian tunneling method to the geoengineering condition evaluation and dynamic controlling method

The new Austrian tunneling method （NATM） is widely applied in design and construction of underground engineering projects. When the type and distribution of unfavorable geological bodies （UGBs） associated with their influences on geoengineering are complicated or unfortunately are overlooked, we should pay more attentions to internal features of rocks grades IV and V （even in local but mostly controlling zones）. With increasing attentions to the characteristics, mechanism and influences of engineering construction-triggered geohazards, it is crucial to fully understand the disturbance of these geohazards on project construction. A reasonable determination method in construction procedure, i.e. the shape of working face, the type of engineering support and the choice of feasible procedure, should be considered in order to mitigate the construction-triggered geohazards. Due to their high sensitivity to groundwater and in-situ stress, various UGBs exhibit hysteretic nature and failure modes. To give a complete understanding on the internal causes, the emphasis on advanced comprehensive geological forecasting and overall reinforcement treatment is therefore of more practical significance. Compre- hensive evaluation of influential factors, identification of UGB, and measures of discontinuity dynamic controlling comprises the geoengineering condition evaluation and dynamic controlling method. In a case of a cut slope, the variations of UGBs and the impacts of key environmental factors are presented, where more severe construction-triggered geohazards emerged in construction stage than those predicted in design and field investigation stages. As a result, the weight ratios of different influential factors with respect to field investigation, design and construction are obtained.

The distribution and availability of phosphorus fractions in restored cut slopes soil aggregates:a case study of subalpine road,Southwest China

The distribution and availability of phosphorus(P)fractions in restored cut slope soil aggregates,along altitude gradients,were analyzed.Samples were collected at 3009,3347,3654 and 3980 m of altitude.We examined soil aggregates total phosphorus(TP),available phosphorus(AP)and phosphorus activation coefficient(PAC),and discovered that there was no significant difference in TP levels between all four altitudes samples(p>0.05).However,there was a significant difference in AP at 3009,3347 and 3980 m of altitude(p<0.05).At the altitudes of 3009,3347 and 3654 m,the AP accumulation in small size aggregates was more advantageous.Overall,PAC dropped steadily as soil aggregates sizes increased,as shown:PAC(3654 m)>PAC(3347 m)>PAC(3009 m)>PAC(3980 m).In all particle size soil aggregates,the distribution of the P fractions was as follows:total inorganic phosphorus(TPi)>total organic phosphorus(TPo)>residual phosphorus(R-P),at 3009,3347 and 3654 m,but a different registry was observed at 3980 m of altitude:TPo>TPi>R-P.Through correlation and multiple stepwise regression analysis,it was concluded that active NaHCO_(3)-Pi was the main AP source.It was also suggested that more attention should be given to the ratio of small particle size aggregates to increase soil AP storage.In order to improve the activation capacity and supply of soil P,along with promotion of the healthy development of soil ecosystem on slope land,it was suggest that inorganic P fertilizer and P activator could be added to soil at both low(3009 m)and high altitudes(3980 m).

Precision Assessment of UAVRS Based DSM in Disaster Emergency

Ground control point (GCP) is important for georeferencing remotely sensed images and topographic model. However, considering that GCP collection is sometimes a difficult, time-consuming and expensive task with high resolution (HR) data in remote and harsh environments, today unmanned aerial vehicle based remote sensing (UAVRS) is frequently used in geological disaster emergency monitoring and rescuing for its great advantage in collecting timely onsite images. In this paper, for evaluating the feasibility of the UAVRS in disaster emergency and high cut slope safety monitoring, the digital surface model (DSM) without GCPs based on Structure from Motion (SfM) is accessed, and results showed that the geometric accuracy of DSM was smaller than 1 percent, which prove the usefulness of DSM based on UAVRS in emergency. Comparing to normal disaster emergency, the method without GCPs can be more efficient and save the disaster emergency time by neglecting GCPs measurement.

Effect of crevice density on biological soil crust development on rock cut slope in mountainous regions,Sichuan,China

Background The rock cut slope(RCS)could cause damage to regional ecological functions and landscapes and requires recovery.Biological soil crusts(BSCs)are pioneer and dominant colonizers during the initial recovery stage.To accelerate the natural recovery of RCS,the development process and influencing agents of BSC should be revealed.Thus,the area index of crevices(IR),BSC coverage(COV)and biomass(BM),soil weight(SW),and major soil nutrients[organic carbon(OC),total nitrogen(TN)and total phosphorus(TP)]content,collected from 164 quadrats on 13 RCSs in the mountainous area of west Sichuan Province,China,were measured,to explore the effect of crevice of RCS on BSC development.Results Soil OC,TN and TP on RCSs ranged from 18.61 to 123.03 g kg^(-1),0.96 to 6.02 g kg^(-1)and 0.52 to 2.46 g kg^(-1),respectively,and were approximately to or higher than those on natural slopes.The OC,TN and TP contents in soils elevated unsystematically with recovery time of RCSs.BSCs on RCS distributed along crevices generally and firstly.During the first 13 years of natural recovery,COV,BM and SW ranged from 6.5 to 28.2%,14.43 to 67.25 g m^(-2),and 127.69 to 1277.74 g m^(-2),respectively.COV,BM and SW increased linearly with IR on RCSs.The positive correlation between COV and BM and IR was insignificantly impacted by bedrock,slope aspect and altitude within the recovery time less than 13 years.COV and BM on RCSs increased significantly when the recovery time is more than 27 years.Conclusions Crevice on RCSs could be a major environmental factor which is conducive to BSC development and soil accumulation through creating a space for water and soil particle.Furthermore,with the increase of recovery time of RCSs,BSCs may grow and reach a stable state with the promotion of soil nutrients,plant growth and microbial activity.These results provide a development process of BSC that from inside to outside the crevices on RCSs.In the areas with stable rock strata and a low risk of geological disasters,purposeful improvement in crevice density on RCS may effectively accelerate BSC development.

Comprehensive Determination of Reinforcement Parameters for High Cut Slope Based on Intelligent Optimization and Numerical Analysis

High cut slopes have been widely formed due to excavation activities during the period of immigrant relocation in the reservoir area of the Three Gorges, China. Effective reinforcement meas-ures must be taken to guarantee the stability of the slopes and the safety of residents. This article pre-sents a comprehensive method for integrating particle swarm optimization （PSO） and support vector machines （SVMs）, combined with numerical analysis, to handle the determination of appropriate rein-forcement parameters, which guarantee both slope stability and lower construction costs. The relation-ship between reinforcement parameters and slope factor of safety （FOS） and construction costs is in-vestigated by numerical analysis and SVMs, PSO is adopted to determine the best SVM performance resulting in the lowest construction costs for a given FOS. This methodology is demonstrated by a prac-tical reservoir high cut slope stabilised with anti-sliding piles, which is located at the Xingshan （兴山） County of Hubei （湖北） Province, China. The determination process of reinforcement parameters is discussed profoundly, and the pile spacing, length, and section dimension are obtained. The results pro-vide a satisfactory reinforcement design, making it possible a signficant reduction in construction costs.